Numerous types and colors of dyestuffs are used in the textile industry for coloration of fibers, yarns, fabrics, etc. in order to impart aesthetic properties to consumer goods. There are myriads of books, publications, patents, etc. that are available describing dyeing processes, methodologies, and equipment used in manufacturing dyed textile goods. A good source of information is contained in a book of papers reprinted from Textile Chemist and Colorist called Dyeing Primer. These papers discuss all the dyestuffs types according to the fibers they are designed to color. Contained in Dyeing Primary, for example, is a paper devoted to dyeing cotton (cellulosic) fibers with Fiber Reactive dyes. There is a paper that addresses dyeing polyarnide fibers such as nylon or wool with Acid dyes. Another paper discusses the use of Basic dyes for dyeing acrylic fibers or “modified” nylon fibers.
The scope of the invention is to minimize the dye loss caused by treatment of finishing agents on Cat-Acid Differentially Dyed (CADD) textile substrates while imparting colorfastness, ozonefastness, and stainresistance. More specifically, the invention addresses the color change caused by the treatment of finishing agents on CADD carpet products manufactured with two classes of dyeable fibers to produce a multicolored carpet style. One class of dyeable fibers, commonly referred to as “acid dyeable fibers” have cationic chemical functionalities which readily accept dyes with anionic chemical functionalities, also commonly referred to as acid dyes. A second class of dyeable fibers, commonly referred to as “cationic dyeable fibers” have anionic chemical functionalities which readily accept dyes with cationic chemical functionalities, also referred to as basic dyes with the basic dyes having poor to marginal colorfastness to ozone.
The problem occurs when CADD nylon carpet styles are treated with a typical stainblocker finishing agent. Conventional stainblockers contain anionic chemical functionalities needed for reaction with acid dyeable nylon fibers. The stainblockers impart to acid dyeable nylon carpets stainresistance to colorants (food grade dyes) contained in food and drink products. Unfortunately, the anionic stainblocker will also remove basic dyestuffs from the cationic dyeable nylon component of a CADD nylon carpet. This dye loss significantly affects the colorfastness of the cationic dyeable nylon fibers to the finishing agent thus the original shade of the carpet. The loss of basic dye can be observed as color bleed in a batch dyebath or in the rinse water depending on the treatment method of the stainblocker. The shade change that occurs is the critical problem. Loss of basic dyestuff lightens the cationic dyeable nylon shade. Any level of basic dye removal that affects the overall shade of the multicolored carpet is unacceptable and precludes the use of a stainblocker finishing agent. At present no CADD nylon carpet products are treated with a stainblocker for stainresistance.
The color loss caused by stainblocking is a serious problem because the inability to use a stainblocker on a carpet product limits that product's marketability. Since 1985 stainblockers have been used to treat acid dyeable nylon carpets in order to prevent colorant stains caused by spills of food and drink products. The original stainblocker was Stainmaster® by DuPont. Today the three prevalent stainblockers are the SAC type, the methacrylate type, and the maleic acid type. Information regarding these stainblockers is disclosed in U.S. Pat. Nos. 4,822,373; 4,875,901; 4,937,123; 5,843,328; 6,814,758 as well as numerous other patents.
In general, stainblockers are applied to acid dyeable nylon fibers. This type of nylon fiber is one of the fibers used in CADD carpet styles. Carpets or carpet yarns made from acid dyeable nylon fibers are either dyed with acid dyes at the carpet manufacturer or dyed by solution dye methods at the fiber producer. In either event stainblockers are applied to the dyed carpets and fixed by either a wet heat treatment method or a dry heat treatment method. The wet heat fixation method is accomplished by either a batch (hot/boiling) water method or continuous steam method. Dry heat fixation is accomplished in drying or coating ovens.
In some carpets stainblockers are not necessary. These are carpets made from cationic dyeable nylon fibers, the other fiber used in CADD carpets. The reason is that unlike acid dyeable nylon fibers which contain amine end groups and are positively charged, cationic dyeable nylon fibers contain sulfonate end groups and therefore negatively charged. Because of ionic fiber/colorant charge repulsion, cationic dyeable nylon fibers have intrinsic stainresistance to acid colorants contained in food and drinks and therefore require no chemical stainblocker treatments. Coloration of cationic dyeable nylon carpets is achieved mostly by using solution dyed nylon fiber supplied by the fiber producer. Some, however, are dyed with acid and pre-metalized acid dyes by the process disclosed in U.S. Pat. No. 5,085,667 at the carpet manufacturer. Regardless of coloration method, basic dyes are not used on cationic dyeable carpets. Only CADD carpets use basic dyes.
CADD carpets are dyed by batch processing using a beck dye machine. The carpet is loaded in the dye machine and water is added. The dyeing procedure is done by adding both acid and basic dyestuffs to the dyebath. Special chemicals are also added in order to stabilize the two dyestuffs. At the end of the dyeing a multicolored carpet style is achieved. After dyeing, the carpet is rinsed, dried, and finished. Because color bleed is problematic, a stainblocker finishing agent cannot be applied, only an anti-soiling finishing agent.
There are economic, logistic, and manpower advantages to being able to produce multicolored carpets using CADD carpet dye methodology versus conventional methods. Conventionally, a multicolored carpet is manufactured by tufting yarns of different colors into a carpet product. This requires that acid dyeable yarns be dyed in yarn dye equipment and solution dyed yarns be purchased from fiber produces. In either event, each yarn color is a separate SKU that must be manufactured or purchased in an amount to correspond to customer orders. Typically excess dyed yarns are produced or purchased and have to be cataloged and inventoried. Most yarn dye equipment requires a good deal of floor space, support equipment, material handling, and personnel.
In CADD carpet styles un-dyed carpet yarns are tufted into a certain pattern style into a big stock item roll, a style SKU. The yarns are un-dyed at this stage. If there is an order, for example, for a certain square yardage of a blue and green multicolored pattern, that amount of square yards is simply pulled from the stock item roll and dyed in one operation in a beck machine. Using the example above, the conventional method would require having two yarn SKUs, one for blue yarns and the other for green yarns. These yarns are tufted into a carpet. The style SKU would be the same for either the CADD or conventional method, but the conventional method would require two yarn SKUs as well as additional manufacturing cost to produce dyed yarns.
The major disadvantage discussed earlier imposed by the use of CADD carpet is that conventional stainblockers cause bleeding of the basic dyes; therefore, CADD styles are not stainresistant to acid colorants as measured by AATCC Test Method 175. This limits their viability for use in the carpet industry.
There have been several efforts to try to impart stainresistance to CADD carpets while trying to prevent the loss of shade due to color bleed. Processes directed to this end are disclosed in U.S. patents and patent application U.S. Pat. Nos. 6,852,134; 6,811,574; 2008/0127430; 2005/0198743; and 2004/0123399. All of these disclosures are directed toward using problematic stainblocker chemistry in methods comprising low temperatures or short dwell time methodologies or reverse application processes. The idea is to try to get an acceptable stain rating by AATCC Test Method 175 while reducing the color loss of the basic dye caused by the stainblocker.
The problem with the inventions disclosed above is that manufacturing plants would have to invest in expensive new equipment that is only useful for CADD carpets or have application procedures that would require exact repeatable process conditions. Neither of these situations is desirable at a carpet manufacturing plant.
In addressing the problem of stainblocking CADD carpets we have discovered a finishing composition that will impart stainresistance and colorfastness to CADD carpet styles without removing any basic dye from the cationic dyeable nylon fibers. Specifically, we have discovered that tannic acid has the ability to impart to CADD carpets stainresistance to acid colorants, neutral colorants, and chemical agents without removing any basic dye from the cationic dyeable nylon fiber portion of the CADD carpet styles. More specifically, tannic acid can be applied to CADD carpet styles by the wet heat fixation methods disclosed in U.S. Pat. No. 6,814,758.